Distillation of tar



INVENTOR W7M w BY 2 Sheets-Sheet ATTQRNEYS S. P. MILLER DISTILLATION OF TAR Filed Jan. 26 1929 Jail/21 W] Jlfly 25, 1933.

y 1933- s. P. MILLER DISTILLATION OF TAR Filed Jan. 26, 1929 2 Sheets-Sheet 2 WWW ATTOR N EY5 5 apparatus.

Patented July 25, 1933 UNITED STATES PATENT OFFICE STUART PARMELEE MILLER, OF ENGLEWOOD, NEW JERSEY, ASSIGNOR TO THE BARRETT COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY DISTILLA'IION or TAR Application filed January 26, 1929. Serial No. 335,206.

This invention relates to improvements in the distillation of tar and the production of distillate oils and pitches therefrom, and it includes improvements in both process and More particularly, the invention comprises improvements in the distillation of tar at coal distillation or gasification and tar production plants.

According to the present invention, the tar to be distilled is heated in an externally heated still, or by indirect contact with heating gases, to a temperature above the boiling point of part of the oils contained in the tar, and the resulting preheated tar is then brought into direct and intimate contact with hot fuel gases, such as coal distillation or carbonization or gasification gases, to effect further distillation of the tar.

More particularly, the present invention comprises an improved process in which the tar is heated continuously in a pipe coil under pressure to a temperature above the boiling point of part of the tar constituents, and then discharged into a still where the preheated tar is brought into direct contact with the hot coal carbonization or asification gases to effect further distillation.

Pipe coil stills have been employed for the distillation of tar by heating the tar continuously in a pipe coil and discharging it into a vapor chamber from which the vapors are drawn off to a condenser and the pitch produced separately drawn off. Such stills are effective for the distillation of part of the oil contained in the tar, but if the tar is heated to a suflicient temperature to produce a high melting point pitch and a high oil yield, the'temperature is such that a considerable decomposition of the oil constituents of the tar takes place, with decrease in oil distilled, and increase in carbon and pitch produced. I

The present invention includes improvements in the operation of such pipe coil stills in which the tar is heated in the pipe coil to a high temperature sufiicient to distill part of the tar constituents, but to a temperature insuflicient to bring about any objectionable decomposition of tar, and is then discharged directly into a still in which the preheated and partly distilled tar is further heated by direct contact with hot coal carbonization or gasification gases, such as coke oven gases, coal gas, water gas, producer gas, etc. The tar can be readily heated to a high temperature and in a continuous manner in the pipe coil and a considerable distillation accomplished without objectionable decomposition, and further distillation can readily be accomplished to produce an increased distillation of oil and the production of a higher melting point pitch by further distillation with the hot gases, while nevertheless avoiding any objectionable or considerable decomposition of heavy oil constituents during such further distillation.

When cold tar is introduced into hot coke oven or other coal carbonization or distillation or gasification gases, a considerable proportion of the heat contained in the hot gases is consumed in heating the tar to the distillation temperature and in dehydrating it. While there is a large amount of heat available in hot coke oven gases or other coal carbonization gases for the distillation of tar, yet the B. t. u. content of the gas per unit volume is relatively low, and the distillation which can be accomplished per unit volume of gas employed is low. When the hot gases are required to heat the tar and dehydrate it in addition to distilling it, a disproportionately large volume of gases is required, and the increase in vapor content of the resulting enriched gases is correspondingly limited, so that it is necessary to employ a correspondingly large volume of gases, and to recover the distillate from admixture with such gases.

The present invention enables the distillation of tar by such hot coal distillation or other hot fuel gases to be very greatly promoted, and, in particular, enables a greatly reduced volume of such gases to be employed to accomplish the desired distillation, and results in a greatly increased enrichment of such gases in oil vapors from the distillation.

The present invention, accordingly, includes improvements in the distillation of tar in pipe coil stills, and also improvements in the distillation of tar by direct contact with hot coal carbonization or other fuel gases, and combines these two processes of distillation in a particularly advantageous manner. Instead of taking off separately and condensing the distillate from the pipe coil still, the vapors from such distillation are discharged into the hot fuel gases and greatly enrich such gases in oil vapors. The distillation by the hot gases is, moreover, greatly promoted by the preheating and partial distillation to which the tar is subjected before it is brought into direct contact with them.

The temperature required for distilling tar to produce a given percentage of distillate and pitch of a given melting point in a pipe coil still is much greater than that required in a still in which the distillation is accomplished by direct contact with hot coal distillation gases. In the pipe coil still it is necessary to heat the tar to. the distillation temperature of the various oils which are distilled, but in the still in which the tar is heated by direct contact with the hot gases, it is only necessary to heat the tar to a temperature somewhat above the dew point of the gases for such oils. Accordingly, when the tar is preheated under pressure to a tems,

perature sufficient to distill part of the oil constituents in the pipe coil still, and when the resulting preheated tar is then discharged into the second still, into direct contact with the hot coal carbonization gases, the preheated tar is superheated from the standpoint of its distillation in the second still. That is, the highly preheated tar discharged from the pipe coil into direct contact with the hot coal carbonization gases is at a much higher temperature than required to produce pitch of the same melting point by distillation directly with such gases. This superheat of the preheated tar therefore assists in the distillation so that less heat is required to be supplied by the hot gases to effect the further distillation. Furthermore, when the tar is preheated under pressure in the pipe coil and then discharged into the still containing the hot gases, there is a resulting flashing of part of the oil when the preheated tar discharges into the gases, and the vapors resulting from this preheating and flashing serve to enrich the gases and vapors produced by further distillation in such still. As a result, it is possible to produce a mixture of gases and vapors from such still which contains a high percentage of oil vapors, and from which mixture the distillate oils can be readily condensed.

The further distillation of the preheated tar by direct contact with the hot gases requires a much lower temperature than would be required in an externally heated still, and

the preheatedand partly distilled tar can readily be further heated and distilled, and a pitch of high melting point produced, to gether with an increased percentage of distillate oil, without heating the pitch to a temperature where any considerable decomposition ot oil takes place. The present process, accordingly, enables tar to be distilled to produce a high percentage of distillate oils, and a high melting point pitch. It also enables tar to be rapidly distilled to produce a lower melting point pitch, and a lower ercentage distillate, with the production 0. gases and vapors greatl enriched in vapors from which the disti late can be readily condensed.

It will be appreciated that, when tar is distilled by direct contact with hot coal carbonization gases, the distillate must be recovered from the gases by cooling the gases to the dew points of the gases for the various oil constituents. Ordinary coke oven gases, for example, contain only around 1% to 3% of vapors, and the dew points of most of the oil constituents contained in the gases is low. However, by preheating the tar according to the present invention and then further distilling it by direct contact with hot coal carbonization gases, the gases can be so greatly enriched in oil vapors that condensation can readily be accomplished at higher temperatures, and the condensation can, moreover, be carried much more nearly to completion. Moreover, the condensation can readily be carried out fractionally so that heavier and lighter oil fractions can be directly condensed.

The tar which is distilled, according to the present invention, may be coke oven tar,

water gas tar, gas retort tar, producergas tar, etc., and it. may be a total composite tar, or a heavier or lighter tar, or blended tars from different sources such as blended water gas and coke oven tar, or coke oven and retort gas tar, etc. The tar distilled is advantageously that produced at the plant at which the distillation is carried out, so that, for example, coal tar produced at a coke oven plant is distilled at the coke oven plant with the use of hot coke oven gases.

The preheating of the tar can readily be carried out at many coke oven or other coal distillation or carbonization plants with the use of waste heat. For example, at a coke oven plant having regenerative preheaters, the flue gases leaving the heating flues of the coke ovens and passing to the stack have a large volume and a temperature, for example, around 400 C. In coke oven plants having recuperative preheaters for the coke ovens the gases pass to the stack at a much higher temperature. Coke oven plants having dry quenching systems have an abundance of heat available for preheating purposes. Where Waste heat gases are not available, the pipe coil can be heated by the combustion of fuel.

\Vhile different types of preheaters can be employed, that which is particularly to be recommended is a pipe coil preheater having a large number of pipes connected together to form a single continuous coil through which the tar is pumped under pressure and in which the tar is gradually heated to the desired temperature. Such a pipe coil can readily be located, for exam le, in a fine through which the hot waste ue gases pass fromthe coke oven heating fiues to the stack. With flue gases available in large quantities at a temperature around 300 to 400 0., and by providing a pipe coil of sufiicient length, the tar can be heated to a high temperature, approximating that of the flue gases, and it can be readily heated to a lower temperature in a shorter pipe coil or at a more rapid rate. The tar can readily be preheated in such a still to a temperature around 200 C. or even to 300 C. or higher.

The gases employed for the further distillation of the preheated tar may be hot coke oven gases, or hot gases from a retort gas plant, or other hot coal carbonization or distillation gases, or producer gas, water gas, etc. Such hot fuel gases are advantageously employed at a high temperature approximating that at which they are produced since with high temperature gases an increased distillation can be accomplished and an increased enrichment of the gases in oil vapors, as compared with lower temperature gases. In the case of coke oven gases, for example, the gases can be withdrawn from the individual coke ovens directly into a still which they enter without material reduction in temperature, for example, at a temperature around 500 to 850 C. or higher, depending upon the type of coke oven, the coking period employed, etc. Even where the gases are partly cooled before being employed for distillation, there will be a greatly increased enrichment of the gases in oil vapors where the tar is reheated in the manner above described be ore it is brought into direct contact with the gases for further distillation.

The light oils distilled from the tar may be to a greater or less extent condensed or scrubbed from the gases, but such light oils as are not so recovered will remain as val-- uable fuel constituents of the gases, giving enriched or carburetted fuel gases.

The further distillation of the preheated tar is accomplished by bringing the tar into direct and intimate contact with the hot gases, for example, by spraying or atomizing the tar or pitch into the gases. While spray nozzles can be employed for introducing preheated tar into the gases, particularly where lower melting point pitches are to be produced, it is more advantageous to em loy mechanical spray devices for repeate ly spraying the tar and pitch into the gases in a thorough-going manner.

In the claims the term tar has been used to cover the tar both in its original state and in a partly distilled condition.

The type of still employed for distilling the preheated tar by direct contact with the hot gases can be varied, depending upon the amount of tar to be distilled, the temperature of the gases available for distillation, etc. A still having suitable mechanical spray devices, such as rapidly rotating rolls or discs, dippin into a body of tar or pitch in the bottom 0 the still, is an advantageous type of still to employ, since by sufiiciently thorough and intensive spraying of the tar and itch into the gases, the gases can be rapidly cooled to a temperature approximatin that to which the pitch is heated, and t e preheated tar can be rapidly distilled.

The tar preheated in the pipe coil can be discharged directly into the still, but it can also, and with added advantage in some cases,-be discharged into a tower throu h which the hot gases and vapors leave t e still, so that the vapors resulting from the preheating will be separated in the tower without entering the still proper, and so that the preheated tar will be further distilled by direct contact with the hot gases and vapors leaving the still before the preheated and partly distilled tar enters the still. In such case, the first heatin will be in the pipe coil under pressure with resulting vaporization of part of the oil on discharge of the reheated tar from the pipe coil, further dlstillation will take place in the tower by direct contact with the hot gases and vapors leaving the still, and the nal distillation will take place in the still itself by direct contact with the hot gases.

Where high melting point pitches are produced, and a high percentage distillate, from the tar, the gases and vapors may leave the still at a high temperature, for example, around 250 to 350 C. They may not be completely saturated with respect to most or all of the vapor which they contain, but a higher degree of enrichment in oil vapors can be obtained by preheating the tar to a high temperature before it is brought into direct contact with the gases. The hot gases and vapors leaving the still, can, as above stated, be employed for further preheating and distilling the already preheated tar. by passing them into indirect contact with tar for preheating the tar, for example, before it passes to the pipe coil still, or even after it has passed through the pipe coil still and before it enters the still containing the hot ases.

The istillate produced by the present They may also be employed process, where the hot gases employed are tar laden gases, may contain some heavy tar or pitch constituents, where the gases are not thoroughly scrubbed and cleaned before condensation, but the percentage of such heavy tar and pitch constituents will be small because of the high enrichment of the gases in oil vapors resulting from the distillation of the tar. Where the gases employed are thoroughly scrubbed and cleaned by the use of an intense and thorough spray of the tar and pitch into the gases, the oil subsequently condensed will be clean oil, i.e. free or substantially so from heavy tar and pitch constituents of a black color.

The cooling and condensation of the distillate from the admixed gases can readily be carried out because of the high percentage of oil vapors contained in the gases. Fractional cooling and condensation can readily be employed, and heavier and lighter oils directly produced, for example, a creosote oil, a tar acid oil, etc.

The extent to which the tar is preheated before introducing it into direct contact with the hot gases can be varied. With Waste heat preheaters, the preheating may be only to temperatures around 150 to 200 C. or it may be up to 300 or 350 C., but in general it should be below the temperature at which any considerable decomposition of the oiltakesplace in the externally heated preheater. When tar preheated to such high temperature is brought into direct contact with hotgases, such as hot coke oven gases, for example, at a temperature of 650 to 850 C., the heat of the hot gases will be employed for distilling the higher boiling oils'from the tar, since the preheating will have resulted in the vaporization of the lower boiling oils. This further distillation by the hot gases can accordingly be carried out so as to produce a high melting point pitch at a sufiiciently low temperature to avoid any considerable decomposition during the distillation, thus giving an unusually high oil yield, and pitch of high melting point representing a relatively small percentage of the tar distilled.

The invention will be further described in connection with the accompanying drawings which are of a more or less conventional and diagrammatic character, and which illustrate apparatus embodying the invention and adapted for the practice of the process of the invention, but it will be understood that the invention is not limited thereto. a

The drawings illustrate the application of the invention to a coke oven plant. It can readily be applied to gas retort plants, or other types of coal carbonization or coal gasification plants.

In the drawings,

Fig. 1 is a plan view of a coke oven plant equipped with distilling means and a tar preheater in which hot waste flue gases are employed for preheating the tar which is fed to the still; and

Fig. 2 shows an elevation partly in crosssection of the apparatus shown in Fig. 1. I A coke oven battery is represented at 5 in which the individual ovens are connected through uptake pipes 6 with the collector main 7 in the usual manner. The gases from the collector main pass through the center-box 8 to a cross-over main 9 and are cooled in condensers 10, all of which apparatus is shown diagrammatically since it may be of the usual and familiar type.

A still 11 is provided in which the hot gases from the "coke ovens are employed to distill tar. The tar entering the still is preheated by hot waste flue gases in the preheater 12. Depending upon the temperature of the flue gases, the rate at which the tar is supplied to the preheater, the size of the coil, etc., the tar may be heated to 200 C. oreven 300 C. or higher.

The waste combustion gases which have been used for heating the coke ovens in the coke oven battery 5 pass through the flue 13 to the stack 14. The flue 13 is provided with a bay-pass in which the preheater 12 is locate This preheater is shown as a pipe coil and should be long enough to preheat the tar to the desired temperature. The valves 14 and 15 are provided for regulating the proportion of the flue gases which are passed over the preheater. By closing the valve 14 and opening the valve 15, all of the gases will pass through the preheater on their way to the stack 1a. A blower 16 may be provided where the insertion of the pipe coils gives added resistance to the passage of the hot gases through the by-pass which it is necessary to overcome.

The tar which enters the preheater through the pipe 17 is passed through the pipe 18 which is preferably insulated as shown at 19 and the preheated tar is fed into the body of the still or, as here shown, into a tower through which the gases and vapors pass on their way from the still to the condensers. As here shown, the preheated tar is sprayed through the spraying means 20 into the gases and vapors leaving the still and vapors are released from the tar and blend with the vapors in the gases in the tower and the tar is further distilled before entering the still due to direct contact with the hot gases and vapors from the still.

The distillation within the still 11 is effected by bringing the tar or partially distilled tar into intimate contact with the hot gases. The hot gases leave the ovens through the uptake pipes 21. By properly manipulating valves in the usual uptake pipes 6- and in the uptake pipes 21, the gases from the ovens connected with the gas header 22 may be directed either into the usual collector main 7 or throu h the uptake pipes 21 into the hot gas eader 22.

This header is insulated as shown at 19 and the still and other parts of the apparatus through which hot tar or hot gases pass may advantageously be insulated where it is desired to prevent loss of heat. The hot gases pass through the gas header 22 into the still 11.

The preheated tar which is sprayed into the tower 23 is topped, i.e., the low boiling oils which have been raised above their boiling point when sprayed into the hot gases and vapors leaving the still, are volatilized and pass over from the tower 23 through the main 24 into the condensers 25 together with the hot gases and vapors from the still. The undistilled tar collects in the bottom of the tower 23 and is drawn off through the line 26 and fed into the still 11 at a point adjacent to that at which the hot gases enter the still from the hot gas header. The partially distilled tar and hot gases pass through the still in a concurrent direction.

The still is provided with means for bringing the tar into intimate contact with the hot gases. It comprises a roll 27 which is so situated that it dips to but a slight extent into the tar or pitch which collects in the bottom of the still. The roll is rotated by the motor 28 at a speed, for example, from 900-1200 B. P. M. This sprays the tar up into the hot gases and the still is filled with an intense spray of tar or pitch. The tar is not only distilled by the ,hot gases but entrained pitch particles carried over into the still by the hit gases are scubbed from the gases and are removed from the still together with the residue from the distillation. The tar may be distilled to a pitch of high melting point in the neighborhood of 300 or 350 F. or even to a pitch of melting point of 400 F. or higher. The still is provided with a trap 29 from which the pitch is drawn oii through the levelling arm 30. By properly adjusting the angle of the arm 30 the level of the pitch within the still may be maintained at the height required to give an intensive spray of tar within the still. The pitch, if of high melting point, may be withdrawn, as here shown, into a trough 31. Cold water supplied from the pipe 32 chills the pitch as it falls into the trough and the pitch is withdrawn in a granulated form into the storage bin 33 from which water may be removed in any suitable manner.

Instead of conveying the pitch into the tower 23, as here shown, so that the low boiling oils will flash and mingle with the gases and vapors from the still, the preheated tar from the pipe 18 may be fed directly into the still at the point where the pipe 26 enters the still and the vapors of the lighter oils may be separated from the high er boiling constitutents within the body'of the still. I I

The condensers 25 may be direct condensers or indirect condensers and means for cooling the gases fractionally to obtain fractional distillates may be employed. The gases and vapors leaving the tower 23 are substantially free from entrained impurities due to the scrubbing action of the intense spray of tar in the still so that clean oils are recovered directly inthe condensers. In the drawings, ordinary condensers of the direct t pe are shown. The drawings show means or drawing ofl' oil from the condensers into the decanter 34 from which the ammonia liquor may be withdrawn through 35 and clean oils will be collected in the oil storage tank 36.

The tar to be distilled is thus heated externally in the preheater '12 to a temperature above the boiling point of the lower boilin constitutents of the tar and after flashing the vapors of the lower boiling constitutents from the higher boiling constituents of the tar in the tower 23, the residue comprising such higher boiling constituents together with particles of pitch, etc. which may settle out of the gases and vapors leaving the still and passing through the tower, or which may be removed from the gases by the scrubbing of the gases and vapors with the residue sprayed into the gases from spraying means 20 which flow down over the baffle mains 37, is conveyed to the still for further distillation.

The invention is not to be considered as limited to the process disclosed in connection with the drawings but is to be construed as defined in the attached claims.

I claim:

1. The method of distilling tar, which comprises heating the tar continuously in a pipe coil to a high temperature, discharging the resulting tar into direct contact with hot coal carbonization or gasification gases in a vapor separating chamber to effect distillation thereof, passing the residue into a still and subjecting it to intimate and thorough contact in the form of a spray with a current of hot coal carbonization or gasification gases to effect further distillation, and passing the resulting gases and vapors through the vapor separating chamher in direct contact with the preheated tar before it enters the still.

2. The method of distilling tar, which comprises preheating the tar continuously in a pipe coil to a temperature above the boiling point of part of the tar constituents, discharging the preheated tar into direct contact with hot coal carbonization gases including the vapors resulting from the preheating of the tar, and cooling the same to condense oils therefrom.

3. The method of distilling tar at a coke oven plant, which comprises preheating tar continuously in a pipe coil still by waste heat gases, introducing the preheated tar into a still into direct contact with a current of hot coke oven gases, thoroughly spraying the gases therein with the tar or pitch to scrub the gases and distill the preheated tar, and drawing off the resulting gases and vapors and cooling the same to condense oils therefrom. v

4. In combination with coal carbonization or gasification apparatus, a tar still a pipe coil preheater, condensers, means or conveying coal carbonization or gasification gases from the carbonization or gasification apparatus to the still and from the still to the condensers, means for introducing tar into the pipe coil heater and for passing the tar from the pipe coil heater intothe still, and means in the still for thoroughly and repeatedly spraying tar or pitch into the gases to effect distillation and to scrub the gases.

5. The method of distilling oils from tar at a coke oven plant, which comprises collecting fresh hot coke oven gases from a plurality of coke ovens in a still, preheating tar in a pipe coil'preheater to a temperature above the boiling point of its lowest boiling constituents, flashing the tar into the still and bringing it into intimate .contact with the hot gases in the still in the form of a fine intense spray, and cooling the resulting gases and vapors to separate oils therefrom.

6. The method of distilling tar at a coke oven plant, which comprises collecting in a still fresh hot coal distillation gases from a plurality of the ovens of the plant in which coal is being distilled, preheating tar in a pipe coil preheater, introducing the preheated tar into the still, thoroughly spraying the gases in the still with the tar to distill it and to simultaneously scrub the gases, and drawing off the resulting gases and vapors and cooling them to condense oils therefrom.

7. The method of producing pitch and oils from tar, which comprises preheating the tar to a temperature suflicient at atmospheric pressure to distill part of the oil constituents from the tar, passing the preheated tar into a still and maintaining a body of the tar therein, repeatedly bringing a portion of the body of tar, while in finely divided hot coal carbonization or gasification gases in the still to distill ofl' oils from the tar and produce a pitch residue that is liquid at the temperature of distillation, flushing the solid surfaces of the still with liquid being distilled, regulating the distillation so as to prevent excessive decomposition of tar constituents and inhibit the formation of coke, and Withdrawing the pitch, while liquid, from contact with the hot gases.

8. The method of producing pitch and oils from tar, which comprises preheating the tar to above about 150 C., passing the preheated tar into a still and maintaining a body of the tar therein, repeatedly bringing a portion of the body of tar while in finely divided form into direct and intimate contact with hot coal carbonization or gasification gases in the still to distill off oils from the tar and produce a pitch residue that is liquid at the temperature of distillation, regulating the distillation so as to prevent excessive decomposition of tar constituents and inhibit the formation of coke, and withdrawing the pitch, while liquid, from contact with the hot gases.

9. The method of producing pitch and oils from tar, which comprises preheating the tar to a temperature suflicient at atmospheric pressure to distill part of the oil constituents from the tar, passing the preheated tar into a still, maintaining a body of the tar therein, repeatedly bringing a portion of the body of tar While in finely divided form into direct and intimate contact with hot coal carbonization or gasification gases in the still to distill oif oils from the tar and produce a pitch residue that is liquid at the temperature of distillation and effecting such contact in such a manner that substantially all heat supplied to said tar during distillation is supplied thereto directly from hot gases in contact therewith, regulating the distillation so as to prevent excessive decomposition of tar 'constitutents and inhibit the formation of coke, and withdrawing the pitch, while liquid, from contact with the hot gases.

10. The method of producing pitch and oils from tar, which comprises preheating the the tar to a temperature between about C. and about350 0., passing the "preheated tar into a still, maintaining a body of the tar therein, retpeatedly bringing a portion of the body 0 tar while in finely divided form into direct and intimate contact with hot coal carbonization or gasification gases form, into direct and intimate contact with ing the distillation so as to prevent excessive decomposition of tar constituents and inhibit the formation of coke, and withdrawing the pitch, while liquid, from contact with the hot gases.

11. The method of producing pitch and oils from tar, which comprises preheating the tar, while under a pressure substantially above atmospheric pressure, to a temperature sufficient at atmosprehic pressure to distill part of the oil constituents from the tar, reducing the pressure on said tar so as to distill off said constituents, passing the resultant tar residue into a still, maintaining a body of the tar residue therein, repeatedly bringing a portion of the body of tar while in finely divided form into direct and intimate contact with hot coal carbonization or gasification gases in the still to distill of]? additional oil constituents from the tar and produce a pitch residue that is liquid at the temperature of distillation, regulating the distillation so as to prevent excessive decomposition of tar constituents and inhibit the formation of coke, and withdrawing the pitch, While liquid, from contact with the hot gases.

12. The method of distilling tar, which comprises heating the tar continuously to a high temperature by passing the tar through a pipe coil in heat exchange relation with hot gases from the heating fines of a coal carbonization or gasification battery, discharging the heated tar into direct contact with hot coal carbonization gases in a vapor separating chamber to effect distillation thereof, passing the residue into a still and subjecting it to intimate and thorough contact in the form of a spray with a current of hot coal carbonization or gasification gases to effect further distillation, and passing the resulting gases and vapors through the vapor separating chamber in direct contact with the preheated tar before it enters the still.

13. The method of producing pitch and oils from tar, which comprises bringing the tar into heat exchange relation with combustion gases while yet hot from the heating fines of the coke ovens of a coke oven plant so as to preheat the tar to a temperature sufiicient at atmospheric pressure to distill part of the oil constituents from the tar, passing the preheated tar into a still and maintaining a body of the tar therein, repeatedly bringing a portion of the body of tar while in finely divided form into direct and intimate contact with hot coal carbonization gases in the still to distill off oils from the tar and produce a pitch residue that is liquid at the temperature of distillation, flushing the solid surfaces of the still with liquid being distilled, regulating the distillation so as to prevent excessive decomposition of tar constituents and inhibit the formation of coke, and withdrawing the pitch, while liquid, from contact with the gases.

STUART PARMELEE MILLER. 

